Titanium alloys and method for manufacturing titanium alloy materials

ABSTRACT

Titanium alloys with a sufficient cold workability and excellent superplasticity characteristics as shown in the (1) and (2) below, and a method for manufacturing a titanium alloy material as shown in the (3) below are provided. (1) A titanium alloy consisting of, by mass %, Al of 2.0 to 4.0%, V of 4.0 to 9.0%, Zr of 0 to 2.0%, Sn of 0 to 3.0% and the balance being Ti and impurities. (2) A titanium alloy consisting of, by mass %, Al of 2.0 to 4.0%, V of 4.0 to 9.0%, Zr of 0 to 2.0%, Sn of 0 to 3.0%, further one or more elements selected from Fe of 0.20 to 1.0%, Cr of 0.01 to 1.0%, Cu of 0.01 to 1.0% and Ni of 0.01 to 1.0%, and the balance being Ti and impurities, wherein Veq obtained by the following equation (1) is in a range of 4.0 to 9.5:
 
Veq=V+1.9Cr+3.75Fe  (1)
where a symbol on a right side of the equation (1) means a content of each element. (3) A method for manufacturing titanium alloy materials, wherein the titanium alloy described in (1) or (2) is subjected to a cold working at a cross-section reduction rate of 40% or more.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to titanium alloys in use in chemicalindustry members such as machine structure members and heat exchangermembers and consumer goods members such as golf clubs, and a method formanufacturing titanium alloy materials. The present inventionparticularly relates to titanium alloys with an excellent coldworkability and superplasticity characteristics, and a method formanufacturing the titanium alloy materials.

BACKGROUND ART

Heat exchangers are instruments capable of transmitting thermal energybetween different fluids. The heat exchangers are used in, for example,air conditioners, refrigerators, air preheating equipment of burners,radiators in automobiles, parts for the chemical industry, parts forseawater and the like. In particular, heat exchangers made of titaniumare used in fields requiring excellent corrosion resistance such as inthe chemical industry or in salt water. In order to reduce the size ofheat exchangers, it is necessary to increase the strength of the partsbeing used and that is why titanium alloy which are light and strong areused as a material for such heat exchangers.

A Ti-6Al-4V alloy has been widely used as the heat exchanger materialdue to its excellent superplasticity characteristics as described in,for example, Non-patent document 1. However, this alloy has poor coldworkability. For example, when thin plates are manufactured by coldrolling the Ti-6Al-4V alloy plate which is wrapped around a coil, thereis a drawback that the number of intermediate annealing needs to beincreased.

Non-patent document 2 shows that a Ti-9V-2Mo-3Al alloy is a titaniumalloy which has an excellent cold workability and also an excellentsuperplasticity workability. However, this alloy contains Mo as anessential element, which results in a high cost of raw materials. Also,because of a high melting point of Mo, there is a higher incidence ofunmelted portions or solidification segregation in melting.

Patent document 1 describes a titanium alloy with excellentsuperplasticity workability containing, by mass %, Al of 5.5 to 6.5%, Vof 3.5 to 4.5%, 0 of 0.2% or less, Fe of 0.15 to 3.0%, Cr of 0.15 to3.0% and Mo of 0.85 to 3.15%, in which Fe, Cr and Mo are within a rangerepresented by a specific equation and an average grain diameter of an acrystal is 6 μm or less. This alloy can be said to be superior to theTi-6Al-4V alloy in the superplasticity workability, but the coldworkability is not considered. Namely, this alloy has a high content ofAl which is 5.5% or more, which results in high deformation resistancein the cold rolling and a high possibility of cracks occurring in theedges of a plate if this alloy is subjected to cold rolling process at across-section reduction rate of 50%.

Patent document 2 describes a titanium alloy with excellent workabilitywhich contains, by mass %, Al of 3.0 to 5.0%, V of 2.1 to 3.7%, Mo of0.85 to 3.15%, O of 0.15% or less, and further one or more elements ofFe, Cr, Ni and Co, in which the content of these elements is in a rangerepresented by a specific equation. There is also described amanufacturing method of a titanium alloy material in a specific hotrolling condition, and a superplastic processing method of the titaniumalloy material in the specific heat treatment condition. However, sincethis alloy contains Mo, there will be the same problem with the alloydescribed in Non-patent document 2.

Patent document 1: Japanese Examined Patent Publication No. 1996-19502B

Patent document 2: Japanese Examined Patent Publication No.1996-23053B

Non-patent document 1: N. Furushiro and three other persons, Titanium'80, 1980, pp. 993-998, published by Metallurgical Society of AIME

Non-patent document 2: T. Oka and 2 other persons, “What is beingstudied about titanium materials in Japan?”, pp. 58-60, edited on Dec.1, 1989 by The Iron and Steel Institute of Japan

DISCLOSURE OF THE INVENTION Problem to be Solved by the Invention

An object of the present invention is to provide titanium alloys withthe excellent cold workability and the superplasticity characteristicsand a method for manufacturing the titanium alloy materials.

Means Adapted to Solve the Problem

The present invention was accomplished as a result of repeated researchmade by the present inventors based on a Ti-3Al-2.5V alloy which is saidto have the excellent cold workability.

The present invention is characterized by titanium alloys as shown in(1) and (2) below, and a method for manufacturing a titanium alloymaterials as shown in (3) below.

(1) A titanium alloy consisting of, by mass %, Al of 2.0 to 4.0%, V of4.0 to 9.0%, Zr of 0 to 2.0%, Sn of 0 to 3.0% and the balance being Tiand impurities.

(2) A titanium alloy consisting of, by mass %, Al of 2.0 to 4.0%, V of4.0 to 9.0%, Zr of 0 to 2.0%, Sn of 0 to 3.0%, further one or moreelements selected from Fe of 0.20 to 1.0%, Cr of 0.01 to 1.0%, Cu of0.01 to 1.0% and Ni of 0.01 to 1.0%, and the balance being Ti andimpurities, wherein Veq obtained by the following equation (1) is in arange of 4.0 to 9.5:Veq=V+1.9Cr+3.75Fe  (1)

where a symbol on a right side of the equation (1) means a content ofeach element.

(3) A method for manufacturing titanium alloy materials is characterizedin that the titanium alloy described in the above (1) or (2) issubjected to the cold working at a cross-section reduction rate of 40%or more.

Effect of the Invention

A titanium alloy of the present invention has a sufficient coldworkability as well as the excellent superplasticity characteristics.Therefore, it is possible to easily produce a coil by the cold rolling,and a material for a super-plastic application, having a uniformdistribution in a plate thickness, can be manufactured. Therefore, it ispossible to easily produce thin plates made of titanium alloy at a lowcost, allowing for the expansion of an application field for thetitanium alloy thin plates.

Best Mode for Carrying Out the Invention

First, chemical compositions in the titanium alloy of the presentinvention and the reasons for the limitation will be described. “%” ineach component means “mass %” in the following explanation.

Al: 2.0 to 4.0%

Al is an element that plays a very important role in increasing thestrength of the titanium alloy. Al is also an effective element forstabilizing the α phase of the titanium alloy. The superplasticitycharacteristics are exhibited in a temperature range in which the ratioof the α phase and the β phase is approximately 50/50. If the content ofAl is low, this temperature range is narrowed, which results indifficulties obtaining stable superplasticity characteristics. Thecontent of Al needs to be 2.0% or more so as to obtain thesuperplasticity characteristics in a wider temperature range. However,the cold workability reduces as the content of Al increases. Inparticular, if a titanium alloy in which the content of Al exceeds 4.0%is subjected to the cold working at a cross-section reduction rate ofabout 50%, the edge cracks occur in the edges of the plate. Therefore,the content of Al is limited to 2.0 to 4.0%.

V: 4.0 to 9.0%

V is an effective element for stabilizing the β phase of titaniumalloys, and has an effect of increasing the ratio of the β phase in atemperature range of about 800 to 850° C. In particular, if the contentof V is 4.0% or more, the temperature range in which the ratio of the αphase and the β phase is approximately 50/50 can be increased. However,if the content of V exceeds 9.0%, oxidation resistance characteristicsof the titanium alloy material are deteriorated. This is because anoxide of V has a sublimation property, so that a scale generated on thesurface of the alloy is not dense but has a high permeability of oxygenif the titanium alloy in which the content of V exceeds 9.0% is exposedto a high temperature. Therefore, cracks occur more easily on thesurface of the alloy, and a high temperature ductility is decreased.Accordingly, the content of V is limited to 4.0 to 9.0%.

Zr: 0 to 2.0%

Zr is an element that may not be necessarily added. If Zr is added, itcontributes to strengthen the titanium alloy due to a solid solutionstrengthening effect thereof If a titanium alloy containing Zr isexposed to the high temperature, a strong Zr oxide is formed on thesurface thereof to suppress oxidation inside the alloy, so that ageneration of the cracks can be prevented in a deformation of thetitanium alloy at the high temperature. Therefore, elongation of thetitanium alloy is increased at the high temperature, and thesuperplasticity characteristics are improved. These effects are largelyexhibited in 0.5% or more. However, Zr is an expensive element, and theoxidation suppression effect described above is saturated if the contentof Zr exceeds 2.0%, leading to a cost increase. Therefore, if Zr iscontained, the content is preferably limited to 2.0% or less.

Sn: 0 to 3.0%

Sn is also an element that may not be necessarily added. Although Sndoes not contributes to stabilize the α phase or the β phase, it is anelement that contributes to strengthen the titanium alloy. To obtainsuch effect of Sn, the content is preferably 0.2% or more. However, ifthe content of Sn exceeds 3.0%, a low melting point region is formed insolidification process, and the cracks occur from this region as astarting point. Therefore, if Sn is contained, the content is preferably3.0% or less.

The titanium alloy of the present invention has the chemicalcompositions described above, and the balance being Ti and impurities.The alloy may contain one or more elements selected from Fe of 0.20 to1.0%, Cr of 0.01 to 1.0%, Cu of 0.01 to 1.0% and Ni of 0.01 to 1.0% assubstitute for a part of Ti. This is based on the following reasons.

Fe and Cr are elements contained, as impurities, in a titanium spongewhich is a titanium raw material, or in an aluminum-vanadium alloy whichis an additional material. Therefore, Fe of less than 0.20% and Cr ofless than 0.01% are contained in the titanium alloy even if theseelements are not positively added. These elements are a β-phasestabilizing element having the same effect as V, but they are cheaperthan V. Accordingly, cost reduction can be realized by positively addingthese elements, so that it is desirable to contain Fe of 0.20% or moreand Cr of 0.01% or more. However, Fe and Cr are a eutectoid type elementforming an intermetallic compound in the titanium alloy. If Fe and Cr ofexceeding 1.0% are respectively contained, there will be embrittlementcaused by excessive precipitations of the intermetallic compound.

Cu and Ni are a β stabilizing element in the same manner with V, and aneffective element to increase the ratio of the β phase in a temperaturerange of 800 to 850° C. These elements are cheaper than V, and can beadded as an alternative element of V. It is desirable to contain Cu of0.01% or more and Ni of 0.01% or more in order to obtain this effect.However, the intermetallic compound is formed and the cold workabilityis lowered if Cu and Ni of exceeding 1.0% are respectively added,because Cu and Ni are the eutectoid type element for titanium.

Accordingly, if one or more elements of these are contained in thetitanium alloy of the present invention, the content is limited to Fe of0.20 to 1.0%, Cr of 0.01 to 1.0%, Cu of 0.01 to 1.0% and Ni of 0.01 to1.0%.Veq(=V+1.9Cr+3.75Fe): 4.0 to 9.5

As an index to exhibit the stability of the β phase in the titaniumalloy, there is a Veq represented by the following equation (1):Veq=V+1.9Cr+3.75Fe  (1)

where a symbol on the right side of the equation (1) means a content ofeach element.

If the Veq is less than 4.0, the ratio of the β phase is lowered in atemperature range of 800 to 850° C., and the superplasticitycharacteristics are hardly exhibited in this temperature range. However,if the Veq exceeds 9.5, the ratio of the α phase is lowed, thesuperplasticity characteristics deteriorate in a temperature range of800 to 850° C. and the specific gravity of the alloy itself increases.Accordingly, if Fe and/or Cr are contained to the titanium alloy of thepresent invention, it is necessary to limit Veq in a range of 4.0 to9.5.

O (oxygen), C (carbon), N (nitrogen) and H (hydrogen) are majorimpurities contained in the titanium alloy of the present invention. Ois an impurity contained in the titanium sponge and a raw material of V,while C and N are impurities contained in the titanium sponge. Also, His an impurity which is absorbed from an atmosphere in heating orabsorbed in an acid pickling process. Impurities are preferably as lowas possible in a range where O is 0.2% or less, C is 0.01% or less, N is0.01% or less, and H is 0.01% or less.

Next, a method for manufacturing titanium alloy materials of the presentinvention will be explained referring to a case of manufacturing a thinplate. An ingot is prepared by an ordinary melting method such as VARand is subjected to hot bloom forging or hot rolling so as to form aslab, after which hot rolling is conducted to prepare a hot coil,followed by the cold rolling to a target plate thickness and annealingto provide the titanium alloy material. The cold rolling is a step thatlargely influences product characteristics, and a titanium alloymaterial with the excellent superplasticity characteristics at the hightemperature can be obtained particularly by the cold working (coldrolling) at the cross-section reduction rate of 40% or more. This isbased on the following reasons.

When the cross-section reduction rate is increased in the cold rolling,a crystal grain diameter in the titanium alloy, particularly a graindiameter of a pro-eutectoid α phase is decreased. Then, if the graindiameter in the titanium alloy is decreased, elongation is increasedupon superplastic deformation at the high temperature, thereby thetitanium alloy material with the excellent superplasticitycharacteristics at the high temperature is exhibited. As describedabove, when the cross-section reduction rate is increased in the coldrolling, the elongation upon superplastic deformation at the hightemperature is sharply increased up to the cross-section reduction rateof about 40%, and less change is observed in a region of 40% or more.

Therefore, in the method for manufacturing the titanium alloy materialsof the preset invention, the cold working is performed at thecross-section reduction rate of 40% or more. Although there is noparticular upper limit in the cross-section reduction rate, when thecold rolling is performed at a cross-section reduction rate of exceeding80%, the edge cracks occur in the edges of the plate. Accordingly, it isdesirable in the cold working to limit the cross-section reduction ratein 80% or less. However, if the intermediate annealing is conducted forthe purpose of recovering the ductility of materials, the cold workingmay be performed in a condition that the cross-section reduction rateexceeds 80%.

The cross-section reduction rate is obtained by the following equation(a).Cross-section reduction rate (%)={(cross-section area beforeworking−cross-section area after working)/cross-section area beforeworking}×100  (a)

EMBODIMENT 1

Using an arc melting furnace of plasma, a button ingot with a width of50 mm, a thickness of 15 mm and a longitude of 80 mm was prepared. Afterthe button ingot was heated at 850° C., it was subjected to hot rollingto prepare a hot-rolled plate with a thickness of 5 mm. After thishot-rolled plate was annealed at 750° C. for ten minutes, an oxide scalewas removed by shot blast and acid pickling, and the surface was furthermachined to a thickness of 4 mm by machining so as to prepare a materialfor the cold rolling. This material was subjected to the cold rolling toprepare a cold-rolled plate with a thickness of 2 mm. At this time, asan evaluation of cold-rolling property, presence of cracks in the edgeson the surface of the cold-rolled plate was performed by visualobservation.

A plate with no cracks in the cold rolling was subjected to a heattreatment in an argon atmosphere at 700° C. for 30 minutes, followed bycold rolling to a thickness of 1.5 mm, and again subjected to the heattreatment in the argon atmosphere at 700° C. for 30 minutes to provide atest specimen. From this test specimen, a plate type test piece with athickness of 1.5 mm and a width of 12.5 mm in a parallel part wasobtained so that the longitudinal direction of the test piece was inparallel to the rolling direction. The distance between gauge marks ofthis tensile test piece was set to be 20 mm, and a tensile test wasconducted at a test temperature of 800° C. and a tensile speed of 9mm/min., so as to measure elongation at fracture.

Table 1 shows chemical compositions of the cold-rolled plate,evaluations of cold rolling property and elongation at fracture. TABLE 1Elongation at Cold rolling fracture Chemical composition (mass %, thebalance being Ti and impurities) property Elongation No. Al V Zr Sn FeCr Cu Ni Veq evaluation (%) Evaluation Remarks 1 1.58* 5.08 — — — — — —5.5 ◯ 180 X Comparative example 2 2.05 4.96 — — — — — — 5.4 ◯ 320 ◯Example of the present invention 3 3.00 4.98 — — — — — — 5.6 ◯ 440 ◯Example of the present invention 4 3.96 4.90 — — — — — — 5.5 ◯ 470 ◯Example of the present invention 5 4.20* 4.94 — — 0.24 — — — 5.8 X — —Comparative example 6 3.01 3.50* — — — — — — 4.1 ◯ 160 X Comparativeexample 7 3.05 4.12 — — — — — — 4.8 ◯ 295 ◯ Example of the presentinvention 8 3.00 7.02 — — — — — — 7.7 ◯ 400 ◯ Example of the presentinvention 9 2.98 8.88 — — — — — — 9.4 ◯ 320 ◯ Example of the presentinvention 10 3.01 5.05 — — 0.50 — — — 6.9 ◯ 355 ◯ Example of the presentinvention 11 3.03 4.98 — — 0.98 — — — 8.7 ◯ 275 ◯ Example of the presentinvention 12 3.02 5.11 — — 1.20* — — — 9.6* ◯ 150 X Comparative example13 2.99 4.97 — — — 0.485 — — 6.3 ◯ 335 ◯ Example of the presentinvention 14 2.97 4.96 — — — 0.95 — — 7.2 ◯ 300 ◯ Example of the presentinvention 15 2.99 5.00 — — — 2.21* — — 9.6* X — — Comparative example 163.02 5.01 — — 0.50 1.15* — — 9.1 X — — Comparative example 17 3.04 4.90— — 0.88 1.01* — — 10.2* ◯ 125 X Comparative example 18 3.03 4.98 0.51 —— — — — 5.5 ◯ 310 ◯ Example of the present invention 19 3.00 5.03 0.95 —— — — — 5.6 ◯ 335 ◯ Example of the present invention 20 3.05 4.98 1.88 —— — — — 5.4 ◯ 340 ◯ Example of the present invention 21 3.00 5.01 — —0.98 — — — 8.7 ◯ 275 ◯ Example of the present invention 22 3.03 5.05 — —— — 0.05 — 5.6 ◯ 420 ◯ Example of the present invention 23 3.01 5.02 — —— — 0.98 — 5.6 ◯ 435 ◯ Example of the present invention 24 3.02 4.98 — —— — 1.13* — 5.6 X — — Comparative example 25 2.99 5.01 — — — — — 0.085.7 ◯ 410 ◯ Example of the present invention 26 3.00 5.03 — — — — — 0.755.7 ◯ 405 ◯ Example of the present invention 27 2.99 5.05 — — — — —1.28* 5.6 X — — Comparative example 28 3.02 4.97 — 0.15 — — — — 5.6 ◯425 ◯ Example of the present invention 29 3.03 5.02 — 0.88 — — — — 5.7 ◯430 ◯ Example of the present invention 30 3.00 5.04 — 1.55 — — — — 5.7 ◯440 ◯ Example of the present invention 31 2.99 4.99 — 2.85 — — — — 5.6 ◯400 ◯ Example of the present invention 32 3.02 5.01 — 3.10* — — — — 5.6X — — Comparative example 33 3.01 6.51 — — 0.90 — — — 9.9* ◯ 170 XComparative example 34 3.21 7.02 — — 0.51 0.45 — — 9.8* ◯ 165 XComparative example 35 3.11 7.55 — — — 0.95 — — 10.0* ◯ 135 XComparative example(1) [*] means outside of the range specified in the present invention(2) [—] in the chemical composition means an impurity level, in which Feis less than 0.20% and other than Fe is less than 0.01%.(3) Examples with [X] in the cold rolling property had no tensile testconducted.

In the cold rolling property evaluation, a plate with no cracks isindicated as [o] and a plate with cracks is indicated as [x] when acold-rolled plate with a thickness of 2 mm was prepared. Also, in theelongation at fracture, a plate of exceeding 200% in elongation atfracture is indicated as [o], and a plate of 200% or less in elongationat fracture is indicated as [x] when a tensile test was conducted at800° C.

As shown in Table 1, alloys satisfying the chemical compositionsspecified in the present invention are capable of being cold rolled toobtain an excellent superplastic elongation.

EMBODIMENT 2

A material for cold rolling containing Al of 3.0%, V of 5.0% and thebalance being Ti and impurities was prepared with a thickness of 4 mm inthe same manner with Example 1.

The material for cold rolling was subjected to a cold rolling indifferent cross-section reduction rates to prepare cold-rolled plateswith thicknesses of 3.5 mm, 3.0 mm, 2.5 mm, 2.0 mm and 1.5 mm. Afterthese cold-rolled plates were subjected to the heat treatment in theargon atmosphere at 700° C. for 30 minutes, a plate type test piece witha thickness of 1.0 mm and a width of 12.5 mm in a parallel part wasobtained so that the longitudinal direction of the test piece was inparallel with the rolling direction. The distance between the gaugemarks in this tensile test piece was set to 20 mm, and the tensile testwas conducted at the test temperature of 800° C. and a tensile speed of9 mm/min., so as to measure the elongation at fracture.

Further, in order to examine the influence of a cross-section reductionrate to the superplasticity characteristics in the cold rolling afterthe intermediate annealing, the cold-rolled plate with a thickness of2.0 mm was subjected to the heat treatment in the argon atmosphere at700° C. for 30 minutes, followed by the cold rolling to a thickness of1.5 mm or 1.0 mm, and again subjected to the hot treatment in the argonatmosphere at 700° C. for 30 minutes so as to prepare a test specimen.From this test specimen, the plate type test piece with the thickness of1.0 mm and the width of 12.5 mm in the parallel part was obtained, andthe same tensile test as described above was conducted to measure theelongation at fracture. Table 2 shows the cross-section reduction rateand the elongations at fracture. TABLE 2 Before intermediate annealingAfter intermediate annealing Plate thickness Cross-section Platethickness Cross-section Elongation rate after cold rolling reductionrate after cold rolling reduction rate at fracture No. (mm) (%) (mm) (%)(%) 36 3.50 12.5 — — 210 37 3.02 24.5 — — 240 38 2.47 38.3 — — 360 391.99 50.3 — — 470 40 1.51 62.3 — — 485 41 2.02 49.5 1.52 24.8 440 422.03 49.3 1.05 48.3 425

As shown in Table 2, since all the examples are within a range of thechemical compositions specified in the present invention, the elongationat fracture exceeds 200% and the excellent superplasticitycharacteristics have been obtained. In particular, the elongation atfracture is increased in accordance with the increase of thecross-section reduction rate, and there is almost no change in theelongation at fracture under a condition that the cross-sectionreduction rate is 40% or more. Also, from the results of No. 39 and No.40, it is understood that an excellent elongation at fracture isobserved if the cross-section reduction rate before the intermediateannealing is 40% or more, even though the cold rolling rate after theintermediate annealing is low.

Although only some exemplary embodiments of this invention have beendescribed in detail above, those skilled in the art will readilyappreciated that many modifications are possible in the exemplaryembodiments without materially departing from the novel teachings andadvantages of this invention. Accordingly, all such modifications areintended to be included within the scope of this invention.

INDUSTRIAL APPLICABILITY

The titanium alloy of the present invention has the sufficient coldworkability as well as the excellent superplasticity characteristics.Accordingly, it is possible to easily prepare the coil by the coldrolling, and also to manufacture a material for a super-plasticapplication having a uniform distribution in a plate thickness.Therefore, the titanium alloy thin plates can be easily manufactured ata low cost, allowing the expansion of the application field for thetitanium alloy thin plates.

1. A titanium alloy consisting of, by mass %, Al of 2.0 to 4.0%, V of4.0 to 9.0%, Zr of 0 to 2.0%, Sn of 0 to 3.0% and the balance being Tiand impurities.
 2. A titanium alloy consisting of, by mass %, Al of 2.0to 4.0%, V of 4.0 to 9.0%, Zr of 0 to 2.0%, Sn of 0 to 3.0%, further oneor more elements selected from Fe of 0.20 to 1.0%, Cr of 0.01 to 1.0%,Cu of 0.01 to 1.0% and Ni of 0.01 to 1.0%, and the balance being Ti andimpurities, wherein Veq obtained by the following equation (1) is in arange of 4.0 to 9.5:Veq=V+1.9Cr+3.75Fe  (1)where a symbol of element on a right side of theequation (1) means a content of the element by mass %.
 3. A method formanufacturing a titanium alloy material consisting of, by mass %, Al of2.0 to 4.0%, V of 4.0 to 9.0%, Zr of 0 to 2.0%, Sn of 0 to 3.0% and thebalance being Ti and impurities, wherein the titanium alloy is subjectedto a cold working at a cross-section reduction rate of 40% or more.
 4. Amethod for manufacturing the titanium alloy material consisting of, bymass %, Al of 2.0 to 4.0%, V of 4.0 to 9.0%, Zr of 0 to 2.0%, Sn of 0 to3.0%, further one or more elements selected from Fe of 0.20 to 1.0%, Crof 0.01 to 1.0%, Cu of 0.01 to 1.0% and Ni of 0.01 to 1.0%, and thebalance being Ti and impurities, wherein the titanium alloy with the Veqobtained by the following equation (1) being in the range of 4.0 to 9.5is subjected to the cold working at the cross-section reduction rate of40% or more:Veq=V+1.9Cr+3.75Fe  (1)where a symbol of element on the right side ofthe equation (1) means a content of the element by mass %.